On 11/14/25 05:11, Viresh Kumar wrote:

On 13-11-25, 19:41, Samuel Wu wrote:

quoted

On Wed, Nov 12, 2025 at 10:45 PM Viresh Kumar [off-list ref] wrote:

quoted

On 12-11-25, 15:51, Samuel Wu wrote:

quoted

The existing cpu_frequency trace_event can be verbose, emitting an event
for every CPU in the policy even when their frequencies are identical.

This patch adds a new policy_frequency trace event, which provides a
more efficient alternative to cpu_frequency trace event. This option
allows users who only need frequency at a policy level more concise logs
with simpler analysis.

Signed-off-by: Samuel Wu <redacted>
---
 drivers/cpufreq/cpufreq.c    |  2 ++
 include/trace/events/power.h | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 4472bb1ec83c..b65534a4fd9a 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c

@@ -345,6 +345,7 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy,
              pr_debug("FREQ: %u - CPUs: %*pbl\n", freqs->new,
                       cpumask_pr_args(policy->cpus));

+             trace_policy_frequency(freqs->new, policy->cpu);
              for_each_cpu(cpu, policy->cpus)
                      trace_cpu_frequency(freqs->new, cpu);

I don't see much value in almost duplicate trace events. If we feel that a
per-policy event is a better fit (which makes sens), then we can just drop the
trace_cpu_frequency() events and print policy->cpus (or related_cpus)
information along with the per-policy events.

Thank you for the feedback Viresh. Fair enough, I've done some testing
and a single trace event should work and would be cleaner. Please let
me know what you think of this proposal for v2.

We can append a bitmask of policy->cpus field to
trace_cpu_frequency(). This way we maintain backwards compatibility:
trace_cpu_frequency() is not removed, and its pre-existing fields are
not disturbed.

Call flow wise, we can delete all the for_each_cpu() loops, and we
still retain the benefits of the trace emitting once per policy
instead of once per cpu.

Fine by me. I have added Scheduler maintainers in the loop to see if they have a
different view.

That's gonna break a lot of tooling but AFAICS that in and of itself isn't
a good enough reason not to do it.
(Added some CCs)